The present invention relates to methods for detecting a fault state in an automated motor vehicle gearbox, and to methods for bringing about a safe state when such a fault state has occurred.
Such a fault-detection method may be applied, in particular, in the field of double-clutch gearboxes.
Double-clutch gearboxes have two parallel component transmissions (branches), which are each assigned a separate friction clutch (dry running or wet running).
The input elements of the friction clutches are connected to a drive unit such as, for example, an internal combustion engine. However, the drive unit can also be an electric motor or a hybrid drive unit.
The uneven gear stages (1, 3, 5, . . . ) are assigned to one of the component transmissions. The even gear stages (2, 4, 6, . . . ) are assigned to the other component transmission.
The driving power is generally transmitted from the drive unit to driven wheels of a motor vehicle via one of the two component transmissions. A gear stage is generally preselected in the respective non-active component transmission. A change of gear speed from the starting gear speed of the active component transmission to the target gear speed of the inactive gearbox can be effected by overlapping activation of the input-side friction clutches. This overlapping activation can be carried out in such a way that there is no interruption in the traction force during the change of gear speed.
The corresponding actuation of the friction clutches and the engagement and disengagement of gear stages generally takes place in an automated fashion by means of a superordinate control unit. This control unit can also be connected to a control unit for the drive unit. In this context, it goes without saying that the control unit selects the torque transmitted via the respective friction clutches and the transmission ratios which have been set up at the respective component transmissions in such a way that said torques and said transmission ratios are adapted to the current driving situation (speed of the vehicle, traction conditions or overrun conditions etc.).
Automated motor vehicle gearboxes have to meet high safety requirements.